Hi Scott,
On 5/27/20, 11:17 AM, "Scott Bradner via Datatracker" <noreply@xxxxxxxx> wrote:
Reviewer: Scott Bradner
Review result: Not Ready
This is an OPS-DIR review of OSPF Link Traffic Engineering Attribute Reuse
(draft-ietf-ospf-te-link-attr-reuse)
This ID describes application-specific attribute advertisements for use in OSPF.
I found this ID hard to read and recommend that it be reviewed for readability.
I have a basic question about this proposal – the ID describes specific
advertisements to be used when particular applications want to make use of
specific link attributes and says that other applications should not make of
the information in the advertisement without saying why such use would be a
problem. I can imagine some reasons but it seems to me that it would be good
if this document just explained the problem it is trying to solve.
We had a lengthy discussion of the requirements in the working group and I'm not sure why you are asking what problem this is solving when it is clearly stated in the abstract and further elaborated in the "Introduction". A side benefit is that we will not have to advertise the OSPF TE LSAs which would need to be correlated with the LSAs for applications. Perhaps that should also be stated. See one more inline below.
Some specific issues in the document
Page 6 – the text says “Standard Application Identifier Bit Mask: Optional set
of bits, where each bit represents a single standard application. Bits are
defined in [I-D.ietf-isis-te-app].” - it seems to me that this should be in an
IANA registry for extensibility but it does not seem to be in the referenced ID
but I could not actually tell
Page 6 – text says “The bits are repeated here for informational purpose”
maybe point to a IANA registry or say “current assignments”
Page 6 – text says “If the link attribute advertisement is limited to be used
by a specific set of applications” - maybe say “intended” rather than
“limited” since I do not see a way to actually limit a future application from
eavesdropping on the advertisement
Page 7 – the text says “If the SABM or UDABM length is other than 0, 4, or 8,
the ASLA sub-TLV MUST be ignored by the receiver.” - it would seem to be
useful operations-wise to say that an indication of an error should be recorded
somewhere
Page 7 – a “User Defined Application Identifier” is introduced but never
described – what uses it and what is it used for
Section 11 – I found this discussion of the relationship between the existence
of a particular advertisement and the possible existence of an application to
use that advertisement to be quite confusing – if the existence of a particular
advertisement does not indicate that any application is listening why not just
say that?
Section 12.1 – it would help to say what problem is trying to be solved – why
is the use of RSVP-TE LSA advertisements a problem?
Perhaps the LSR WG COULD have solved the problem with the existing RSVP-TE LSAs. However, this was not the consensus of the WG and the, IMO, the resultant encodings would have been sub-optimal. The resultant information would have been spread over more LSAs and you would have more chicken and egg situations with the correlation of LSAs. Now, with OSPFv3 Extended LSAs, all the required information is advertised in a single LSAs.
Thanks,
Acee
Section 12.3.3 – I could not tell if this section is saying that the
application specific attribute advertisements could not be used if there is
even a single legacy router present of if the presence of such a router means
that the application specific attribute advertisements can be used but the old
advertisements must also be used Section 14 – it might help to say how new
Sub-TLV types can be added to the registry
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